The invention relates to methods and apparatus for cleaving optical fibers. More particularly, the invention relates to cleaving of optical fibers using dual, opposing cutter means*.
*The terms xe2x80x9ccuttingxe2x80x9d and xe2x80x9ccutterxe2x80x9d as used herein are intended to refer to the action of the cutter means resulting in the cleaving of the fiber. 
Optical fibers are gaining increasing use in diverse applications, particularly in telecommunications and waveguides, wherein light energy is transmitted through long distances within the optical fibers with little or no concomitant energy losses. Devices which employ optical fibers often must be coupled one to another, and such coupling requires the severance and the reconnecting thereof of the transmitting fibers. Optical fibers are, generally, made of glass, which material presents a unique set of problems associated with the severing and reconnecting of such fibers. Loss of light energy at a coupling is detrimental to most transmissions and is to be avoided.
A junction between light fibers should be as near-perfect as possible; that is, the glass-to-glass interface should abut precisely one fiber to another, to minimize energy losses and signal imperfections at these junctures. To accomplish precise joining, a precision cleaving tool must be employed.
Miles of optical fibers are installed xe2x80x9cin the fieldxe2x80x9d, that is, far removed from precision instrumentation. Various cleaving tools have been devised for field use, which provide various degrees of acceptability for the cleaved joint and for ease of operation, which also is of paramount importance in field use. Repeatability and consistency in cleavage are also important considerations for any tool.
The usual method of severing a glass fiber involves placing it under tension, as by bending, and nicking the fiber at a point of highest tension in the bend arc. An optical fiber which is bent and then scribed or nicked will break (sever) at the scribe as a result of the variation in tensile stress across the cross-section of the fiber created by the bend. The break will be in the brittle mode and leave only slight imperfections across the fiber cross-section, which can then be removed by polishing, to produce an acceptable, virtually imperfection-free surface and subsequent joint.
An example of a known scribe-and-break tool for field use is found in U.S. Pat. No. 5,301,868. That patent discloses a scribe-and-break tool for fracturing the free end of an optical fiber said to be suitable for hand-holdable configurations and field use. The tool has an elongated body and a plunger that actuates a blade for scribing the free end of an optical fiber retained in tension within a depressible head that extends outwardly from the body. The free end of the optical fiber contacts the blade, thereby scribing the free end of the fiber causing the free end to break off.
See also the patents referred to and distinguished in U.S. Pat. No. 5,301,868, especially U.S. Pat. No. 5,063,672, which discloses an alternative hand held tool for scoring and severing an optical fiber and is also said to be suitable for field use.
My prior U.S. patent application, Ser. No. 09/414,581, discloses and claims a device for cleaving optical fibers which, in a hand-held unit suitable for field use, provides for the sequential bending and cutting of a fiber resulting in a precise cut extending across the fiber perpendicularly to the fiber axis.
In contrast to prior devices which operate, generally, in the xe2x80x9cbend-and-nickxe2x80x9d mode, the present invention provides apparatus in which the fiber is not purposely bent to induce tension. Further, with the present device, while precise and perpendicular cuts may be achieved, in addition angled cleaves become possible. These cleavages are achieved through use of dual, opposing, cooperatively operable cutting means reciprocally moving in a xe2x80x9cpinchxe2x80x9d mode to sever and cleave a fiber, all in contrast to the prior art xe2x80x9cbend-and-nickxe2x80x9d devices.
Reciprocating blades are known in glassmaking processes wherein a stream of molten glass is cut into discrete charges known as xe2x80x9cgobsxe2x80x9d. See, for example, U.S. Pat. No. 3,962,939. Such cutting of glass streams generally results in troublesome imperfections in the final product known as xe2x80x9ccutter marksxe2x80x9d, and such imperfections must be subsequently removed or cured before use. See, for example, U.S. Pat. No. 3,160,493.
In contrast to these known prior devices, the present invention provides apparatus and methods for cleaving optical fibers, specifically solid glass fibers, using dual, opposing, reciprocally operable cutting means which provide cleaves heretofore unachievable and greatly improved over those attainable with the previously known devices.
Apparatus is provided for cleaving optical fibers. The apparatus includes a housing assembly having an opening therein for receiving an optical fiber to be cleaved, and dual, opposing, cooperatively operable cutting means reciprocally moveable in opposite directions substantially transversely to the longitudinal axis of an optical fiber inserted into and through the opening and exiting between the dual cutting means. The cutting means are mounted in adjacent proximity to the exit of the opening. Upon insertion of an optical fiber through the opening and into the housing, and upon actuation of the cutting means, the fiber is cleaved.
The cutting means preferably are diamond knives.
The fiber to be cleaved may be sheathed within insulation or contained within a connector such that the fiber extends outwardly from either exposing a free end thereof. The opening has a diameter large enough to receive the fiber but is smaller than the insulation or connector diameter, which effectively prevents the insulation or connector from insertion into the opening in the housing. Upon actuation of the cutting means, a predetermined, exposed length of fiber extending beyond the insulation or connector, equal to the predetermined distance between the entrance to the opening and the cutting means, is cleaved.
The fiber may be a glass fiber, and in a typical installation the fiber is a glass fiber encased in polymeric insulation or a ceramic ferrule and the cutting means is positioned within the housing so as to effect cutting a predetermined length of fiber extending from and exposed from the ferrule or insulation.
The glass fiber to be cleaved may have a diameter of approximately 125 micrometers or less, to and including approximately 250 micrometers and up to approximately 3 millimeters. For fibers extending from connectors, the predetermined cleave length, that is, the length of exposed fiber extending backwardly from cleave to ferrule, may be a length within a range of up to 500 micrometers, is typically a length within the range of 25 to 250 micrometers, and for many applications is about 100 micrometers. In the case of insulated fibers not contained in connectors, the predetermined cleave length, that is, the length of exposed fiber extending backwardly from cleave to insulation, may be a length within the range of up to 50 millimeters, is typically within the range of 0 to 20 millimeters and for many applications is about 10 millimeters.
In this apparatus, each of the dual cutting means may be spring-mounted; for example, each may be mounted on a leaf spring wherein both leaf springs are identical having the same spring constant. This preferred embodiment of the apparatus is such that each cutting means is manually operable, in the simplest form by the thumb and forefinger action of an operator acting, respectively, on each of the dual, reciprocally moveable leaf springs.
In an alternate embodiment, also preferred, the apparatus may have dual, reciprocally moveable cutting means which are cam-actuated. Such mechanically actuated apparatus may include a housing assembly which is generally cylindrical in shape and, optionally, has removably connected thereto a receptacle for receiving and collecting cut ends of a plurality of cleaved fibers.
The apparatus may include dual, opposing, reciprocally moveable diamond knives oriented such that the blade edge of each is perpendicular to the longitudinal axis of the fiber. Alternatively, the blade edge of each knife may be oriented at an angle offset from the perpendicular to the longitudinal fiber axis, to effect an angled cleave. The cleave angle is generally less than 45xc2x0 and, for typical applications, is less than 10xc2x0.
The apparatus may include a cleave-length-determining, removably affixed fitting mounted adjacent to the entrance of the housing opening and having a longitudinal orifice extending therethrough. The orifice corresponds to and acts cooperatively in line with the opening in the housing, and has a desired, pre-set, effective bore length. Upon actuation of the cutting means, with the fiber inserted to the hilt formed by the insulation (or ferrule, as the case may be), the optical fiber is cleaved, leaving a predetermined length of bare fiber corresponding to the effective bore length exposed from the cleave backwardly to the insulation (ferrule). This apparatus may have a plurality of interchangeable such fittings, each having a desired pre-set bore length.
The apparatus may have a housing assembly fabricated of aluminum, plastic, or other suitable material, and a preferred plastic is glass filled polycarbonate.